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Anomalocaris
Anomalocaris is an extinct genus of anomalocaridid,which are,in turn,thought to be closely related to the arthropods.The first fossils of Anomalocaris were discovered in the Ogygopsis Shale by Joseph Frederick Whiteaves,with more examples found by Charles Doolittle Walcott in the famed Burgess Shale.Originally several fossilized parts discovered separately were thought to be three separate creatures,a misapprehension corrected by Harry B. Whittington and Derek Briggs in a 1985 journal article. Anatomy '' ''Anomalocaris is thought to have been a predator.It propelled itself through the water by undulating flexible lobes on the sides of its body.Each hole sloped below the one more posterior to it,and this overclapping allowed the lobes on each side of the body to act as a single fin,maximzing the swimming efficiency.The construction of a remote-controlled model showed this mode of swimming to be intrinsically stable,meaning that Anomalocaris need not have had a complex brain to cope with balancing while swimming.The widest part of the body was on the third to fifth lobe; it narrowed towards its tail,and had at least 11 lobes in total.The more posterior lobes are difficult to discriminate,making an accurate count difficult.Anomalocaris had a large head,a single pair of large,compound eyes on stalks comprising approximately 16,000 individual lenses,and an unusual,disk-like mouth.The mouth was composed of 32 overlapping plates,four large and 28 small,resembling a pineapple ring with the center replaced by a series of serrated prongs.The mouth could constrict to crush prey,but never completely close,and the tooth-like prongs continued down the walls of the gullet.Two large'arms' with barb-like spikes were positioned in front of the mouth.The tail was large and fan-shaped,and along with undulations of the lobes,was probaly used to propel the creature through Cambrian waters.Stacked lamella of what were probaly gills attached to the top of each lobe. For the time in which it lived Anomalocaris was a truly gigantic creature,reaching lengths of up two metres. Discovery Anomalocaris has been misidentifiend several times,in part due to its makeup of a mixture of mineralized and unmineralized body parts; the mouth and feeding appendage was considerably harder and more easily fossilized than the indicate body.Its name originates from a description of a detached 'arm',described by Joseph Whiteaves in 1892 as a separate crustacean-like creature due to its resemblance to the tail of a lobster or shrimp.The first fossilizied mouth was discovered by Charles Doolittle Walcott,who mistook it for a jellyfish and placed it in the genus Peytoia.Walcott also discovered a second feeding appendage but failed to realize the similarities to Whiteaves' discovery and instead identified it as feeding appendage or tail of extinct Sidneyia.The body was discovered separately and classified as a sponge in the genus Laggnia; the mouth was found with the body,but was interpreted by its discoverer Simon Conway Morris as an unrelated Peytoia that had through happenstance settled and been preserved with Langgania.Later,while clearing what he thought was an unrelated specimen,Harry B. Whittington removed a layer of covering stone to discover the unequivocally connected arm thought to be a shrimp tail and mouth thought to be a jellyfish.Whittington linked the two species,but it took several years for researchers to realize that the continuously juxtaposed Peytoia,Langgania and feeding appendage actually represented a single,enormous creature.According to International Commission on Zoological rules,the oldest name takes priority,which in this case would be Anomalocaris.The name Langgania was later used for another genus of anomalocarid.Peytoia''has been modified into Parapeytoia,a genus of Chinese anomalocarid.Anomalocaris is placed in extinct family Anomalocaridae,and is considered to be related to modern arthropods. Stephen Jay Could cities Anomalocaris as one of the fossilized extinct species he belived to be evidence of a much more diverse set of phyla that existed in the Cambrian era,a conclusion disputed by other paleontologists. In 2011,six fossils of compound eyes date to the Cambrian period were recovered from archaeological dig at Emu Bay on Kangaroo island.The eyes were the first found belonged to Anomalocaris,proving that Anomalocaris was indeed an arthropod as has been suspeted.The find also indicated that advanced arthropod eyes able to ''tell friend or foe and detect features of environment had the evolution of jointed legs or hardened exoskeletons.The eyes were 30 times powerful than those of Trilobites,long thought to have had the most advanced eyes of any contemporary species and which are thought to be able to sence only night or day.With 30,000 lenses,the resolution of the 3 centimetres wide eyes would have been rivalled only by that of the modern Dragonfly which has 28,000 lenses in each eyes. Ecology '' '' Anomalocaris had a cosmopolitan distribution in Cambrian seas,and has been found from early to mid Cambrian deposits from Canada,China,Utah and Australia,to name but a few. A long-standing view holds that Anomalocaris fed on hard-bodied animals,including trilobites.While its mid-gut glands strongly suggest a predator lifestyle,its ability tp penetrate mineralised shells has come under fire in recent years.Some Cambrian trilobites have been found with roung or W-shaped bite marks,which were identifiend in shape with the mouthparts of Anomalocaris. Stronger evidence that Anomalocaris ate trilobites comes from fossilised faecal pellets,which contain trilobite parts and are so large that the anomalocaris are the only organisms large enough to have produced them.However,since Anomalocaris lacks any mineralised tissue,it seemed unlikely that it would be able to penetrate the hard,calcifiend shell of trilobites.One possibility is that anomalocaris fed by grabbing one end of their prey in their jaws while using their appendages to quickly rock the other end of the animal back and forth.This produced stresses that exploited the weaknesses of arthropod cuticle,causing the prey's exoskeloton to rupture and allowing the predator to access its innards.This behavior is thought to have provided an evolutionary pressure for trilobites to roll up,to avoid being flexed until they snapped.However,the lack of wear on anomalocaroid mouthpart suggest they did not come into regular contact with mineralised trilobite shells.Computer modeling of the Anomalocaris mouthparts suggests they were in fact better suited to sucking on smaller,soft-bodied organisms. ''The mouthparts of Anomalocaris are in fact not tetraradial like 'Peytoia',but have three major axes and a small central opening;thus this species probaly fed by sucking up small items rather than biting hard-bodied organims ''